I did a bit of research and I'm still just as lost as to what exactly it is. Apparently it's supposed to make the drawings pop and give it a sense of realism but I'm lost as to how to achieve that effect.

I work regular shading by thing about 1 light source (or 2 if I want to have a backlight) . Ambiant occlusion is When 2 Surfaces or more are very closed so Light can't go easyly to there (sorry for my bad english ^^'.By the way you don't need direct light to make ambiant occlusion, you can paint it before or after direct light and shading.